In telecommunication networks, it is necessary to guarantee service to users even in case of failure of network's equipments.
This problem is particularly perceived in geographically distributed networks wherein the great physical distance between network equipments makes a technical failure more probable.
If a user requests some services to a network server which is no more available (for instance because of server breakdown or connection problems) the network needs to replace this server with another operating one, called backup server.
Typically, known distributed backup solutions make use of a primary server and a backup server connected to each other by means of a telecommunication network.
Clients query the primary server in order to receive a service; in case of failure of the primary server, a backup algorithm redirects traffic on the backup server.
A typical example of these backup solutions is provided for databases, like MySQL (MySQL Cluster NDB 7.2, http://dev.mysql.com/doc/refman/5.5/en/mysql-cluster.html), wherein, in order to increase service availability and to reduce failure recovery time, a plurality of geographically distributed servers is used. One server acts as a master directly receiving the queries from the clients. By using proprietary algorithms and protocols, a copy of the queries and of the database changes is provided to other backup servers via a TCP/IP network; these backup servers are therefore kept in a state which is coherent with the current state of the master server. In case of failure of the master server, new queries are redirected to one of the backup servers which wakes-up and replies to the new queries, therefore providing service continuity to the clients.
US patent application US 2008/0114827 A1 discloses a backup solution for a distributed server system which comprises a primary manager, one or more backup servers and one or more work servers. The primary manager distributes service requests to the backup servers, which, in turn, deliver them to the work servers that execute the requested service. Primary manager associates a state identifier to each service request, so that all backup servers store a corresponding state of the primary manager. In case of failure of the primary manager each backup server can replace the primary manager. Backup servers aggregate replies outputted by the work servers and send these replies to the primary manager.
Once each backup server has completed the operation associated with a command of the primary manager, it sends a success or failure message to the primary manager. If one of the backup servers or one of the workers is not responding, the primary manager may generate a new service request to assign the work of the not responding backup server or work server to other backup servers or work servers.
US patent application US 2006/019834 describes an apparatus and a method for improving intercell handover of a wireless network, i.e. the process of transferring an ongoing call or data session from one access point to another one. Access points and mobile terminals are provided with a communication interface with an intermediate OSI layer having a buffering function, called Intermediate Buffer Management Layer, IBML. This intermediate layer is below the third OSI layer and maintains a copy of data packets transmitted through the lower layers. When the access point in use detects a forthcoming handover, the content of its own buffering layer is transferred to the buffering layer of the next access point which the mobile terminal is connecting to.
US 2007/0214196 A1 discloses systems and methods for providing a federated backup involving coordination and synchronization of backup and restore operations among a plurality of hosts to ensure data consistency. A master node (backup host) acts as a controller for the entire backup and restore operation. All other application hosts of the network execute backup and restore operation according to the master node inputs. All hosts are connected via Ethernet links.